Wacker-type alkene oxidation to carbonyl compounds is one of the most important oxidation reactions in synthetic chemistry and pharmaceutical industry (Smidt et al. Angew. Chem. (1959), Vol. 71, page 176; Smidt et al. Angew. Chem. Int. Ed. Engl. (1962), Vol 1, page 80; Tsuji, Synthesis (1984), page 369; Tsuji, (1998) Palladium Reagents and Catalysts Innovation in Organic Synthesis; John Wiley & Sons, New York). Conversion of alkenes RCH═CH2 to acetaldehyde (R═H) or methyl ketones (R≠H) through Wacker process (FIG. 1a) has been well documented by Smidt and Tsuji; however, highly selective formation of aldehydes from catalytic oxidation of RCH═CH2 (R≠H) without C═C bond cleavage (FIG. 1b) remains a challenge. Previous work by Feringa (Feringa, Chem. Commun. (1986), page 909), Murahashi (Murahashi et al., Chem. Commun., (1991), page 1559), and Wenzel (Wenzel et al. Chem. Commun. (1993), page 862) showed that oxidation of aliphatic alkenes (such as oct-1-ene and dec-1-ene), N-allyl amides/lactams, and allyl esters with O2 or air in the presence of certain palladium or palladium/copper catalysts affords a mixture of aldehyde and methyl ketone products. Recently, Ho and co-workers reported palladium/copper-catalyzed oxidation of a few 1,5-aliphatic dienes with O2 to form aldehydes in 60-99% yields (Ho et al. Tetrahedron Lett. (2003), Vol. 44, page 6955).
In efforts to develop new oxidation technology based on ruthenium porphyrin catalysts, we found that the oxidation of a wide variety of terminal alkenes with 2,6-dichloropyridine N-oxide (Cl2pyNO) in the presence of dichlororuthenium(IV) porphyrin catalysts [RuIV(por)Cl2] (por=tdcpp 1, tmp 2, where H2tdcpp=meso-tetrkis(2,6-dichlorophenyl)porphyrin and H2tmp=meso-tetramesitylporphyrin) produced aldehydes in up to 99% yields with 100% substrate conversion without C═C bond cleavage. The present invention describes the first ruthenium-catalyzed “Wacker-type oxidation” of terminal alkenes (Hirobe et al., Heterocycles (1995), Vol. 40, page 867; Groves et al., J. Am. Chem. Soc. (1996), Vol. 118, page 8961; Berkessel et al., J. Chem. Soc. Perkin Trans. 1 (1997), page 2265; Che et al., Chem. Commun. (1998), page 1583; Che et al., J. Org. Chem. (1998), Vol. 63, page 7364; Gross et al. Org. Lett. (1999), Vol. 1, page 2077; Gross et al., Inorg. Chem. (1999), Vol. 38, page 1446; Che et al., J. Am. Chem. Soc. (2000), Vol. 122, page 5337; Che et al., J. Org. Chem. (2001), Vol. 66, page 8145; Che et al., Chem. Eur. J. (2002), Vol. 8, page 1554; Che et al., Org. Lett. (2002), Vol. 4, page 1911; Che et al., Chem. Commun. (2002), page 2906; Berkessel et al., Chem. Eur. J. (2003), Vol. 9, page 4746; Simonneaux et al., J. Mol. Catal. A (2003), Vol. 206, page 95; Gray et al., Inorg. Chim. Acta (1998), Vol. 270, page 433), which apparently proceeded by a different mechanism from those proposed for the palladium- or palladium/copper-catalyzed reactions reported by the respective groups of Feringa, Murahashi, Wenzel and Ho. The realization of a one-pot diazoacetate olefination directly from aldehyde substrates generated in-situ from this ruthenium-porphyrin-catalyzed alkene oxidation reaction is also reported herein.